Instantaneous - Depth measured below water line or instantaneous water body surface

Parameters

BODC CODE

Rank

Units

Short Title

Title

ADEPZZ01

1

Metres

DepBelowSurf

Depth below surface of the water body

BOTTFLAG

1

Dimensionless

C22_flag

Sampling process quality flag (BODC C22)

CPHLSPP1

1

Milligrams per cubic metre

LorSpec_Chl-a_>GFF

Concentration of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and spectrophotometry and processing following the Lorenzen protocol

PHAESPP1

1

Milligrams per cubic metre

LorSpec_Phae_>GFF

Concentration of phaeopigments {pheopigments} per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and spectrophotometry and processing following the Lorenzen protocol

SAMPRFNM

1

Dimensionless

SampRef

Sample reference number

Definition of Rank

Rank 1 is a one-dimensional parameter

Rank 2 is a two-dimensional parameter

Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Open Data supplied by Natural Environment Research Council (NERC)

Niskin Bottle

The Niskin bottle is a device used by oceanographers to collect subsurface seawater samples. It is a plastic bottle with caps and rubber seals at each end and is deployed with the caps held open, allowing free-flushing of the bottle as it moves through the water column.

Standard Niskin

The standard version of the bottle includes a plastic-coated metal spring or elastic cord running through the interior of the bottle that joins the two caps, and the caps are held open against the spring by plastic lanyards. When the bottle reaches the desired depth the lanyards are released by a pressure-actuated switch, command signal or messenger weight and the caps are forced shut and sealed, trapping the seawater sample.

Lever Action Niskin

The Lever Action Niskin Bottle differs from the standard version, in that the caps are held open during deployment by externally mounted stainless steel springs rather than an internal spring or cord. Lever Action Niskins are recommended for applications where a completely clear sample chamber is critical or for use in deep cold water.

Clean Sampling

A modified version of the standard Niskin bottle has been developed for clean sampling. This is teflon-coated and uses a latex cord to close the caps rather than a metal spring. The clean version of the Levered Action Niskin bottle is also teflon-coated and uses epoxy covered springs in place of the stainless steel springs. These bottles are specifically designed to minimise metal contamination when sampling trace metals.

Deployment

Bottles may be deployed singly clamped to a wire or in groups of up to 48 on a rosette. Standard bottles have a capacity between 1.7 and 30 L, while Lever Action bottles have a capacity between 1.7 and 12 L. Reversing thermometers may be attached to a spring-loaded disk that rotates through 180° on bottle closure.

CTD Calibration Sample Data Set as part of the North Sea Project

Document History

Converted from CDROM documentation.

Sampling strategy and methodology

During the North Sea Project a significant data set of samples used to calibrate the CTD sensors accrued. This document describes the methods used to obtain these data.

Salinity

A salinity sample, usually from the bottle fired nearest to the sea floor, was drawn from each cast after several washings with the sample sea water into a screw topped glass bottle with an airtight plastic seal. Samples were transferred in batches to the ship's constant temperature laboratory where they were left for at least 24 hours to attain thermal equilibrium.

Salinities were measured on a Guildline Autosal salinometer using standard sea water as a reference standard. Occasionally, if supplies of standard sea water ran low, batches of sea water calibrated against standard sea water were used as a secondary standard.

Quality control comprised the rejection of salinity values shown to be erroneous during the CTD calibration exercise.

Temperature

On each CTD cast one of the sample bottles (usually the first to be fired at the bottom of the cast) was fitted with a frame containing two SIS RTM-4002 digital thermometers which reversed, triggering the thermometers, when the bottle was fired.

The readings were corrected using manufacturers calibration sheets. If the calibrated values differed by more than 0.009C, the data were checked and erroneous values rejected. Checks were also made to eliminate erroneous data resulting from failure to reset the thermometers between casts. The two values (if both deemed good) were averaged. Any further values shown to be erroneous during the CTD calibration exercise were deleted from the data set.

Dissolved Oxygen

Three replicate samples were drawn from the water bottles into 60 ml borosilicate glass stoppered bottles and 0.5ml of each Winkler reagent added using BCD multi-addition pipettes. The reagents were prepared according to the recommendations of Carrit and Carpenter (1966). After mixing, the oxygen bottles were stored under fresh water until analysed.

Analysis was undertaken on board using the manual photometric endpoint detector method described by Bryan et al (1976).

Chlorophyll and Phaeopigment

Extracted chlorophyll and phaeopigments for all cruises where chlorophylls were done with the exception of CH72A and CH72C were determined in the same laboratory, Plymouth Marine Laboratory, using the following protocol.

Up to 2 litres of water for each sample were filtered through glass fibre filters (GFF) and frozen quickly on board ship. The samples were returned frozen to the laboratory where they were extracted with 90% acetone and assayed in a scanning spectrophotometer. The concentrations of chlorophyll and phaeopigments were calculated using the SCOR-UNESCO algorithms (Strickland and Parsons, 1968).

The chlorophyll and phaeopigment determinations on the two legs of Challenger 72 (A and C) in 1990 were undertaken by a different group using a totally different protocol as follows.

Up to 0.5 litres of sea water were filtered through Whatman GFF filters taking care to avoid unnecessary exposure to light. Filters were then extracted, on board ship, in the dark in 90% Analar grade acetone, 10% distilled water, neutralised with sodium bicarbonate.

Fluorescence was measured at sea using a Turner Designs bench fluorometer, calibrated using spectrophotometrically determined standards, before and after acidification with 8% HCl. Chlorophyll and phaeopigment concentrations were calculated using the equation in Tett (1987). The resulting measurement of 'chlorophyll' is the sum of chlorophyll-a and chlorophyllide-a.

Total and Organic Sediment

Two litres of water were drawn from each CTD bottle into a large measuring cylinder. Each sample was filtered using a vacuum filtration system onto a pre-weighed filter. On the early cruises (CH28, CH33, CH35, CH37 and CH39) Nucleopore filters were used. On later cruises these were replaced by GFF filters. Each sample was carefully washed with distilled water to remove salt, removed from the filtration system and air dried.

In some cases where samples had a large sediment load it proved impossible to filter two litres. In these cases, as much of the sample as possible was filtered and the volume filtered determined by noting the volume of water remaining in the measuring cylinder.

After the cruise, each sample was dried and reweighed to constant weight to give the total suspended matter concentration. The samples were then ashed and the organic sediment content obtained from the loss of weight on ignition. The polycarbonate Nucleopore filters used at the beginning of the project decomposed on ignition. Consequently, there are no organic sediment data for project cruises before Challenger 41.

North Sea Project

The North Sea Project (NSP) was the first Marine Sciences Community Research project of the Natural Environment Research Council (NERC). It evolved from a NERC review of shelf sea research, which identified the need for a concerted multidisciplinary study of circulation, transport and production.

The ultimate aim of the NERC North Sea Project was the development of a suite of prognostic water quality models to aid management of the North Sea. To progress towards water quality models, three intermediate objectives were pursued in parallel:

Production of a 3-D transport model for any conservative passive constituent, incorporating improved representations of the necessary physics - hydrodynamics and dispersion;

Defining a complete seasonal cycle as a database for all the observational studies needed to formulate, drive and test models.

Proudman Oceanographic Laboratory hosted the project, which involved over 200 scientists and support staff from NERC and other Government funded laboratories, as well as seven universities and polytechnics.

The project ran from 1987 to 1992, with marine field data collection between April 1988 and October 1989. One shakedown (CH28) and fifteen survey cruises (Table 1), each lasting 12 days and following the same track, were repeated monthly. The track selected covered the summer-stratified waters of the north and the homogeneous waters in the Southern Bight in about equal lengths together with their separating frontal band from Flamborough head to Dogger Bank, the Friesian Islands and the German Bight. Mooring stations were maintained at six sites for the duration of the project.

Table 1: Details of NSP Survey Cruises on RRS Challenger

Cruise No.

Date

CH28

29/04/88 - 15/05/88

CH33

04/08/88 - 16/08/88

CH35

03/09/88 - 15/09/88

CH37

02/10/88 - 14/10/88

CH39

01/11/88 - 13/11/88

CH41

01/12/88 - 13/12/88

CH43

30/12/88 - 12/01/89

CH45

28/01/89 - 10/02/89

CH47

27/02/89 - 12/03/89

CH49

29/03/89 - 10/04/89

CH51

27/04/89 - 09/05/89

CH53

26/05/89 - 07/06/89

CH55

24/06/89 - 07/07/89

CH57

24/07/89 - 06/08/89

CH59

23/08/89 - 04/09/89

CH61

21/09/89 - 03/10/89

Alternating with the survey cruises were process study cruises (Table 2), which investigated some particular aspect of the science of the North Sea. These included fronts (nearshore, circulation and mixing), sandwaves and sandbanks, plumes (Humber, Wash, Thames and Rhine), resuspension, air-sea exchange, primary productivity and blooms/chemistry.

Table 2: Details of NSP Process cruises on RRS Challenger

Cruise No.

Date

Process

CH34

18/08/88 - 01/09/88

Fronts - nearshore

CH36

16/09/88 - 30/09/88

Fronts - mixing

CH56

08/07/89 - 22/07/89

Fronts - circulation

CH58

07/08/89 - 21/08/89

Fronts - mixing

CH38

24/10/88 - 31/10/88

Sandwaves

CH40

15/11/88 - 29/11/88

Sandbanks

CH42

15/12/88 - 29/12/88

Plumes/Sandbanks

CH46

12/02/89 - 26/02/89

Plumes/Sandwaves

CH44

13/01/89 - 27/01/89

Resuspension

CH52

11/05/89 - 24/05/89

Resuspension

CH60

06/09/89 - 19/09/89

Resuspension

CH48

13/03/89 - 27/03/89

Air/sea exchanges

CH62

05/10/89 - 19/10/89

Air/sea exchanges

CH50

12/04/89 - 25/04/89

Blooms/chemistry

CH54

09/06/89 - 22/06/89

Production

In addition to the main data collection period, a series of cruises took place between October 1989 and October 1990 that followed up work done on previous cruises (Table 3). Process studies relating to blooms, plumes (Humber, Wash and Rhine), sandwaves and the flux of contaminants through the Dover Strait were carried out as well as two `survey' cruises.

Table 3: Details of NSP `Follow up' cruises on RRS Challenger

Cruise No.

Date

Process

CH62A

23/10/89 - 03/11/89

Blooms

CH64

03/04/90 - 03/05/90

Blooms

CH65

06/05/90 - 17/05/90

Humber plume

CH66A

20/05/90 - 31/05/90

Survey

CH66B

03/06/90 - 18/06/90

Contaminants through Dover Strait

CH69

26/07/90 - 07/08/90

Resuspension/Plumes

CH72A

20/09/90 - 02/10/90

Survey

CH72B

04/10/90 - 06/10/90

Sandwaves/STABLE

CH72C

06/10/90 - 19/10/90

Rhine plume

The data collected during the observational phase of the North Sea Project comprised one of the most detailed sets of observations ever undertaken in any shallow shelf sea at that time.

North Sea Project Frontal Process Study

The nearshore, mixing and circulation fronts studies all concerned the front extending from the region of Flamborough Head offshore between summer stratified water to the north and well mixed water to the south. The associated local circulation and distinctive dispersion, notably by eddies exchanging material across the front, are important to North Sea transports of all water-borne constituents. In collaboration with MAFF, moorings were laid and CTD, ADCP and SeaSoar surveys carried out to define the dynamical fields for model testing and interpretation. Near shore HF radar gave synoptic coverage of large scale and eddy contributions to transport. Further offshore drogue tracks and the spreading of released Rhodamine B was used both to assess circulation and horizontal and vertical mixing.

Moorings were deployed at five stratified sites (FA, FB, FC, DA and DB) to study the circulation in the frontal area.

The deployment history is summarised below:

Site

Position

Rig

DeploymentDate

Comments

FA

53° 59.87'N, 000° 09.43'E

56381

09 July 1989

FB

54° 03.45'N, 000° 17.42'E

56382

09 July 1989

FC

No data returned

DA

54° 53.98'N, 001° 11.70'E

56386

11 July 1989

Transmissometer mooring lost

DB

54° 55.05'N, 001° 04.06'E

56388

11 July 1989

North Sea Project Resuspension Process Study

The ratio of particulate to dissolved material which is so important to water quality is affected by resuspension which, in turn, depends on the character of the sea bed, biological influences, tidal currents, wind, wave and seasonal stratification. The objectives of the three resuspension cruises were to make time series observations of physical, sedimentological and biological properties of the sediment, suspended particle material and water at two sites in the North Sea, using a variety of moored instruments, CTD/water bottle casts, pumped sampling and sediment grabs and box cores.

The two sites were:

Northern Site

54° 35'N, 004° 50'E

45m depth

muddy sand

seasonally stratified water column

Southern Site

52° 40'N, 003° 40'E

27m depth

sand

permanently well-mixed water column

North Sea Project Sandwaves and Sandbanks Process Study

Sandwave fields cover at least 15000 km2 of the Southern Bight of the North Sea. Drag coefficients based on measured pressure gradients were recorded and sea bed photography used to test bedload prediction formulae. The sand covering much of the southern North Sea is mobile forming banks that are interleaved with mud. Current meter moorings placed either side of a bank were used to estimate its associated circulation and contribution to dispersion. A 3 dimensional model using wave-current interaction enhancing bed stress is being applied to fine grid (~100m) bathymetry and is being tested using detailed measurements of near-bed currents and turbulence obtained from the STABLE (Sediment Transport And Boundary Layer Equipment) rig.

North Sea Project Plumes Process Study

Estuaries are important boundary sources of some metals and nutrients in the North Sea and distinctive dispersions in their plumes such as the Humber, Wash and Thames outflow, required special study.

Specific objectives included

the definition of the spatial and temporal characteristics of the Humber/Wash and Thames by repetitive sampling for selected conservative and non-conservative constituents around a grid enclosing the plume

the determination of the transport pathways for non-conservative constituents in relation to suspended particle/water exchanges

the characterisation of nutrient and metal transfer across the sediment/water interface

These latter two were carried out through controlled experiments on-board ship. Nutrient flows were correlated with river flows using all available data. A 2-dimensional hydrodynamic model was used to calculate nutrient fluxes and mass balances.

North Sea Project Primary Productivity Process Study

The planktonic ecosystem in the North Sea is fuelled largely by local primary production. The aim of this study was

to measure primary productivity and relate it to physical conditions, light, nutrients, and organic fluxes

to determine horizontal and vertical distribution, and behaviour of zooplankton in relation to hydrographic conditions and phytoplankton

North Sea Project Air-Sea Exchanges Process Study

Air-sea exchange rates are important for determining the budgets of carbon dioxide, oxygen and some metals held within the sea. The primary aim of these cruises were

to measure the rate of gas exchange across the sea surface as a function of wind and sea conditions by the release of volatile tracers into the water column

to investigate the rates of dispersion and advection due to tidal and residual currents by means of the same tracer release

to investigate the biological sources of oxygen, methane, dimethyl sulphide and a suite of halocarbons in the coherent body of water marked by the tracers, with a view to obtaining budgets

North Sea Project Blooms/Chemistry Process Study

This study examined the effects of developing phytoplankton blooms on water chemistry. Time series measurements using drogued buoys (primary production, dimethyl sulphide and vertical fluxes) were recorded on a diatom bloom off the North Yorkshire coast and a Phaeocystis bloom in the Southern Bight. The aim was

to investigate gross and net primary production during bloom conditions

to examine the relationships between primary productivity and biogeochemical cycling of certain trace metals and biogenic traces gases

Please note:the supplied parameters may not have been sampled from all the bottle firings described in the table above. Cross-match the Sample Reference Number above against the SAMPRFNM value in the data file to identify the relevant metadata.